1. Field of the Invention
The invention relates in general to a portable electronic system, and more particularly to a multi-function high speed bus with less number of pins and the accessing method of the portable electronic system.
2. Description of the Related Art
The advance of technology matures the development of portable electronic devices. For example, portable electronic devices are designed with size decreasing and function increasing. Portable electronic devices, such as mobile phones, personal digital assistants (PDAs), or PDA mobile phones serve to provide communication, information looking up, and entertainment. The busy modern people require more and more readily accessible information, and therefore, portable electronic devices are becoming an indispensable necessity for the life of modern people.
The design of portable electronic device, for example PDA, is usually small and light for easy carrying. Expansion pack is used when other expansion device, such as memory card, network card, or data card, is required. The interface between the electronic device and the expansion pack can be, for example, PCMCIA/CF or variable latency I/O (VLIO). Due to the widespread usage of PDAs, manufactures try to develop different kinds of expansion devices, which adopt PCMCIA/CF interface or VLIO interface, in order to supply expandable function to the users.
However, the size of the connector required by both the VLIO interface and the PCMCIA/CF interface is too large, and does not fit in well with the trend to go smaller and lighter for portable electronic devices. The VLIO interface, which is the interface used by INTEL Xscale processor, includes 8 control lines, 32 data lines, and 26 address lines—there are totally 66 lines required by the VLIO interface, and the size of the connector between the electronic device and the expansion pack is very large. The PCMCIA/CF interface also requires many transmission lines and its connector is very large, too.